Rubber hardened by over-vulcanization is largely manufactured under the name of ebonite or vulcanite.
M and M' are two permanent magnets; P and P' are soft iron pole-pieces upon which are placed the electromagnet coils C and C'; D is the diaphragm; I is a soft iron distance piece placed between the magnets at the end remote from the diaphragm; B is the brass body of the instrument, over which is placed a thin ebonite shell S.
E is the ear-piece made of ebonite; F is a cap of the same material enclosing the receiver terminals, which are mounted upon the ebonite block G, attached to the distance piece I.
Rollers are made to adhere to their metal spindles by the intervention of a layer of ebonite, and after vulcanization they are turned.
Ebonite takes a fine polish, and is valuable to the electrician on account of its insulating properties, and to the chemist and photographer because vessels made of it are unaffected by most chemical reagents.
A little instrument, supplied by Hartmann and Braun, contains a short length of fine bismuth wire wound into a flat double spiral, half an inch or thereabouts in diameter, and attached to a long ebonite handle.
Many modifications have been patented by Hermite, that of 1895 specifying the use of platinum gauze anodes, held in ebonite or other frames.
Rub the sheet of ebonite vigorously with warm flannel and lay it rubbed side downwards on the top of the tray.
Touch the tray with the finger for an instant, and lift up the ebonite without letting the hand touch the tray a second time.
If the electrified tray is touched with the sealing-wax or ebonite rod, it will not be discharged, but if touched with a metal wire, the hand, or a damp thread, it is discharged at once.
Rub the sheet of ebonite with flannel, lay it face downwards on one tray, touch that tray with the finger for a moment and lift up the ebonite sheet, rub it again, and lay it face downwards on the second tray and leave it there.
- Let one tray be insulated as before, and the electrified sheet of ebonite held over it, but not allowed to touch the tray.
If the ebonite is withdrawn without touching the tray, the latter will be found to be unelectrified.
If whilst holding the ebonite sheet over the tray the latter is also touched with an insulated brass ball, then this ball when removed and tested with the electroscope will be found to be negatively electrified.
Again, if, whilst holding the electrified ebonite over the tray, we touch the latter for a moment and then withdraw the ebonite sheet, the tray will be found to be positively electrified.
The electrified ebonite is said to act by " electrostatic induction " on the tray, and creates on it two induced charges, one of positive and the other of negative electricity.
The last goes to earth when the tray is touched, and the first remains when the tray is insulated and the ebonite withdrawn.
Charge positively a brass ball held on an ebonite stem, and introduce it, without touching, into the canister.
The last elaboration of the insulated slip water-bottle by Ekman, Nansen and Pettersson has produced an instrument of great perfection, in which the insulation is effected by layers of water between a series of concentric ebonite cylinders, all of which are closed both above and below when the apparatus encloses a sample, and each of which in turn must be warmed considerably before there is any rise of temperature in the chamber within.
In front of them a disk of ebonite or glass, having carriers of metal fixed to its edge, was rotated by a winch.
The standpoint is that of the peculiar Judaizing or Ebonite Christianity due to persistence among Christians of the tendencies known among pre-Christian Jews as Essene.
They are produced as follows: A sharp-pointed needle is placed perpendicular to a non-conducting plate, such as of resin, ebonite or glass, with its point very near to or in contact with the plate, and a Leyden jar is discharged into the needle.
In series in the order, 1000, 100, 10, i; 1, 10, 100, 1000, the junctions between each pair being connected to brass blocks, a series of which are mounted upon an ebonite slab that forms the lid of the box.
Hence according to the magnitude of each coil the total resistance may be made anything from I to 9, 10 to 90, or 100 to goo ohms, &c. Three or four of the " dials " thus composed are arranged side by side, the brass blocks being mounted on a slab of ebonite and the coils contained in the box underneath, and they are so joined up that the central block of one dial is connected to the outside block of the next marked O.
By introducing perforated shields of ebonite between the electrodes, so that the full current-density was only attained at the centres of the jets, these ill effects could be prevented.
In other cases, Leyden jars or condensers take the form of sheets of mica or micanite or ebonite partly coated with tin foil or silver leaf on both sides; or a pile of sheets of alternate tin foil and mica may be built up, the tin foil sheets having lugs projecting out first on one side and then on the other.
An ebonite beam B is rocked up and down rapidly by a train of mechanism, and moves the cranks FIG.